He wasn't toying with their lives, he had given them a chance to survive, of course, he would use the victors as his test subjects, he will transform them into mindless killing machines that would only listen to his command.
He left the place and immediately, the demons inside started fighting each other, some started to race after the location of the weapons scattered everywhere, it was hectic.
Outside, the demons that were recruited by Shadowslash wanted to watch the battle, demons are beings that loved to cause chaos.
It's in their blood to wreck havoc, fortunately, they are quite loyal to their lord, not one of them dares to break their formation.
Shadowslash looks at them and said, "You can watch them but don't interfere, only the strongest and smartest demon will survive and given a new lease to life."